The MIMO (Multiple-Input Multiple-Out-put) technology is first put forward by Marconi in 1908. A wireless communications system may use the MIMO technology to receive and send a signal. The MIMO technology comprehensively utilizes information about a wireless channel, such as a coverage area, a spectrum utilization, and a channel capacity. A next-generation wireless broadband mobile communications system uses the MIMO technology, that is, multiple antennas are disposed at an end of a base station, multiple antennas are also disposed at a mobile station, and an MIMO communication link is formed between the base station and the mobile station.
At a transmit end or a receive end of an actual MIMO system, transmission from a baseband to an antenna port passes through a related radio frequency circuit, causing inconsistency of amplitudes, phases, and delays between channels of antennas, which severely reduces an actual effect of MIMO transmission. Therefore, in the MIMO system, transmit channel correction and receive channel correction of a device need to be performed. Similarly, in the MIMO system, reciprocity correction of a transmit channel and a receive channel also needs to be performed, that is, difference correction of amplitudes, phases, and delays of the transmit channel and the receive channel. An objective of all the channel correction is to enable amplitudes, phases, and delays of transmit channels, or of receive channels, or of a transmit channel and a receive channel to keep consistent between each other.
FIG. 1a is a structural block diagram for existing correction inside a board of a transmit channel and a receive channel. As shown in FIG. 1a, a structure of correction inside a board in the prior art may include: a baseband unit 10, transmitters 12, receivers 13, a directional coupler 14 and a directional coupler 15, a combiner 16, a splitter 17, a correction transceiver 18, a correction calculation unit 19, and a multi-antenna array 11.
When a device transmits a service signal, after being processed by the baseband unit 10, the service signal is fed into a corresponding transmitter 12. The transmitter 12 converts a baseband signal into an analog radio frequency signal, and the analog radio frequency signal is transmitted to wireless space by using the multi-antenna array 20. Meanwhile, the directional coupler 15 couples some transmit signals output by the transmitters 12 at each antenna port, and after being combined by the multi-port combiner 16, the transmit signals are fed into the correction transceiver 18 and are forwarded to the correction calculation unit 19 by the correction transceiver 18. In this way, the correction calculation unit 19 can calculate to obtain differences of amplitudes, phases, and delays between transmit channels of the transmitters 12, the differences are finally fed back to the baseband unit 10 by the correction calculation unit 19, and the baseband unit 10 adjusts, according to a feature of the differences calculated by the correction calculation unit 19, an amplitude, a phase, and a delay of each antenna, so as to finally enable amplitudes, phases, and delays of signals transmitted at antenna ports to keep consistent.
Similarly, when a device receives a service signal, the multi-antenna array 11 receives a wireless service signal from the wireless space, and a receive channel of a receiver 13 converts a radio frequency analog signal into a normal service baseband signal and sends the normal service baseband signal to the baseband unit 10. Meanwhile, the correction transceiver 18 sends a receiver correction reference signal, the receiver correction reference signal is divided by the multi-port divider 17 into multiple same correction reference signals, then some correction reference signals are coupled by the directional coupler 15 at each antenna port and fed into each receiver 13, and the baseband unit 10 sends the coupled correction reference signals output by receivers 13 to the correction calculation unit 19. The correction calculation unit 19 calculates according to the correction reference signals output by the receivers 13 to obtain differences of amplitudes, phases, and delays between receive channels of the receivers 13, the differences are finally fed back to the baseband unit 10, and the baseband unit adjusts, according to a feature of the differences calculated by the correction calculation unit 19, an amplitude, a phase, and a delay of each receive antenna, so as to finally enable amplitudes, phases, and delays of signals received by the antenna ports to keep consistent after the signals pass through radio frequency channels.
It can be known from FIG. 1a that, in the foregoing structure, when transmit channel correction of transmitters is performed inside a board, signals of the transmitters are processed by using a channel on which the directional coupler 14 and the combiner 16 are located; while when receive channel correction of receivers is performed, a receiver correction reference signal of the correction transceiver is processed by using a channel on which the divider 17 and the directional coupler 15 are located. However, in an existing system, accuracy of channel reciprocity correction of a transmitter and a receiver is not high. Reciprocity refers to that, when locations of input and specific output of a network are exchanged, the output is not changed because of this type of location exchange.